Liquid level height inspection device

Abstract

To recognize the inclination of a liquid level by the rotation of a rotator and inspect the height of the liquid level correctly.SOLUTION: A liquid level height inspection device images a liquid level of liquid inclined in a container 1 with the centrifugal force by the rotation of a rotator and recognizes the liquid level height of the liquid from a photographed image. Imaging means is provided on the inner side of a conveyance path of the container 1 to image an arcuate section A formed by the edge of the inclined liquid level. Image processing means comprises: a radius calculation unit which recognizes an approximate circle C for the arcuate section A and calculates a radius R of the approximate circle C; a temporary liquid level height calculation unit which calculates a temporary liquid level height from the arcuate section A; a correction value storage unit which stores the radius R of the approximate circle C and a correction value N measured by the experiment; and an actual liquid level height calculation unit which calculates the actual liquid level height H by using the radius R of the approximate circle C and the correction value N.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a liquid level height inspection device, and more particularly to a liquid level height inspection device that photographs the liquid level in a container inclined by the centrifugal force caused by the rotation of a rotating body and recognizes the liquid level height of the liquid in the container.

Background Art

[0002] Conventionally, after filling a container such as a plastic bottle with a liquid such as a beverage, it is necessary to inspect whether the liquid is filled with an appropriate amount. As such a filling amount inspection method, a method of inspecting the height of the liquid level in the container is known. On the other hand, for the conveyance of the above container, a rotating body having a holding portion for holding the container formed on its outer periphery is used, and the container is conveyed along an arc-shaped conveyance path by rotating the rotating body. When the container is conveyed by the rotating body in this way, the liquid level of the liquid is inclined by the centrifugal force caused by the rotation of the rotating body. Therefore, a liquid level height inspection device that inspects the liquid level height while considering the inclination of the liquid level is known (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above Patent Document 1, the inclination angle of the liquid level is calculated by photographing the container from the conveyance direction, and the liquid level height is measured by applying a correction value corresponding to the inclination angle. However, when the rotating body is rotated at a high speed, the liquid level does not become flat but curves (see FIG. 3(b)), and the inclination angle cannot be accurately recognized. In view of such problems, the present invention provides a liquid level height inspection device capable of accurately measuring the liquid level height of a liquid in a container from an image of the liquid surface inclined by the centrifugal force acting on the container.

Means for Solving the Problems

[0005] That is, the liquid level height inspection device according to the invention of claim 1 includes a rotating body having a holding part for holding a container filled with a liquid, imaging means for imaging the container conveyed by the rotating body, and image processing means for performing image processing on the image captured by the imaging means. In the liquid level height inspection device, the imaging means images the liquid surface inclined inside the container by the centrifugal force caused by the rotation of the rotating body, and the image processing means recognizes the liquid level height of the liquid in the container from the captured image. The imaging means is provided inside or outside the conveyance path of the container to image the arc-shaped part formed by the edge of the inclined liquid surface. The image processing means includes a radius calculation part that recognizes an approximate circle of the arc-shaped part and calculates the radius of the approximate circle, a temporary liquid level height calculation part that calculates a temporary liquid level height from the arc-shaped part, a correction value storage part that stores a correction value set based on the radius R of the approximate circle and the liquid level height measured by experiment, and an actual liquid level height calculation part that corrects the temporary liquid level height calculated by the temporary liquid level height calculation part using the radius R of the approximate circle calculated by the radius calculation part and the correction value of the correction value storage part, and calculates the actual liquid level height.

Advantages of the Invention

[0006] According to the invention of claim 1, the liquid surface inclined by the centrifugal force caused by the rotation of the rotating body is imaged by the imaging means provided inside or outside the conveyance path of the container, so that the arc-shaped part formed by the edge of the liquid surface is recognized. Furthermore, the radius of the approximate circle for the arc-shaped portion is obtained, and the height of the virtual liquid surface is calculated. The actual liquid surface height is calculated by correcting the height of the virtual liquid surface with a correction value obtained through experiments. That is, even if the inclined liquid surface is not flat, it is possible to inspect the height of the liquid surface based on the inclination of the liquid surface.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0008] The following is an explanation of the illustrated embodiments. FIG. 1 shows a plan view of a liquid surface inspection device 2 provided in a filling line for filling a container 1 such as a PET bottle with a liquid such as a beverage. FIG. 2 shows a cross-sectional view of the II-II portion in FIG. 1. The liquid surface inspection device 2 of this embodiment determines the quality of the liquid filling amount by detecting the height of the liquid surface of the liquid filled in the container 1. It includes a rotating body 3 for transporting the container 1, a photographing means 4 for photographing the container 1 transported by the rotating body 3, and an illumination means 5 for irradiating light onto the container 1, and these are controlled by a control means (not shown). Upstream of the liquid level height inspection device 2, there are filling means for filling the container 1 with liquid and a capper for attaching a cap to the container 1. The liquid level height inspection device 2 is filled with liquid and the container 1 with a cap attached is supplied thereto. Also, downstream of the liquid level height inspection device 2, there are reject means for rejecting the container 1 based on the inspection result by the liquid level height inspection device 2, a caser for housing the container 1 in a case, and the like.

[0009] As shown in FIG. 2, the container 1 is made of a transparent material such as PET or glass, and includes a main body portion 1a for housing liquid, a cap 1b attached to the mouth portion, and a neck portion 1c formed between the main body portion 1a and the mouth portion. Here, since the liquid level of the liquid filled in the container 1 is located near the neck portion 1c and the cross-sectional shape of the neck portion 1c is circular, the liquid level in the neck portion 1c is formed in a circular shape along the inner wall surface of the container 1.

[0010] A supply wheel 6 and a discharge wheel 7 are provided on the upstream side and the downstream side of the rotating body 3, respectively. The supply wheel 6 is supplied with the container 1 before inspection from a supply conveyor 6a, and the container 1 after inspection is discharged from the discharge wheel 7 to a discharge conveyor 7a. As shown in FIG. 2, holding portions 8 for holding the container 1 are provided at equal intervals on the outer periphery of the rotating body 3. The holding portions 8 include a placement plate 8a on which the container 1 is placed and a top locator 8b that abuts on the container 1 placed on the placement plate 8a from above. The container 1 is conveyed in a state of being sandwiched between the placement plate 8a and the top locator 8b.

[0011] When the container 1 is conveyed by the rotating body 3 having the above configuration, the container 1 is conveyed along an arc-shaped conveyance path, and a centrifugal force due to the rotation of the rotating body 3 acts on each container 1, causing the liquid level S of the liquid filled in the container 1 to incline. When the container 1 is viewed from the conveying direction, as shown in FIG. 3, it is inclined such that the outer peripheral side of the rotating body 3 at the liquid surface S is positioned upward. When the container 1 is viewed from the center side of the rotating body 3, as shown in FIG. 4, the liquid surface S has a substantially elliptical shape. Furthermore, as shown in FIGS. 3 and 4, when the rotational speed of the rotating body 3 is changed, the conveying speed of the container 1 can be changed. However, since the centrifugal force acting on the container 1 also fluctuates at that time, the inclination angle of the liquid surface S fluctuates between the case (a) where the rotational speed is low and the case (b) where the rotational speed is high. In particular, as shown in FIG. 3(b), when the rotational speed of the rotating body 3 is increased, the liquid surface S is curved and the liquid surface S is no longer flat, making it difficult to accurately measure the inclination angle of the liquid surface S.

[0012] As shown in FIG. 2, the photographing means 4 and the lighting means 5 are provided along the conveying path of the container 1 in the rotating body 3. Among these, the photographing means 4 is provided on the center side of the rotating body 3 with respect to the container 1, and the lighting means 5 is provided on the outer peripheral side. A conventionally known CCD camera can be used for the photographing means 4, and the photographed image is transmitted to the image processing means 11 provided in the control means. The lighting means 5 irradiates light, for example, by an LED, and may irradiate X-rays in addition. With such a configuration, when the container 1 conveyed by the rotating body 3 passes between the photographing means 4 and the lighting means 5, since the photographing means 4 photographs the container 1 from the inside of the conveying path, it is possible to photograph the substantially elliptical liquid surface S as shown in FIG. 3 above. However, since the light irradiated by the lighting means 5 passes through the transparent container 1 while being blocked by the liquid, the portion of the liquid contained in the container 1 is photographed dark, and the space above the liquid is photographed bright. As a result, among the elliptical shape indicating the liquid surface S, the lower side portion is hidden in the dark portion indicating the liquid, and the upper side portion in the substantially elliptical shape is photographed as the arc-shaped portion A. Incidentally, the photographing means 4 may be provided on the outer peripheral side of the rotating body 3, and the lighting means 5 may be provided on the central side. Even in this case, the arc-shaped portion A can be photographed by the photographing means 4 from the outer peripheral side of the rotating body 3.

[0013] The image processing means 11 includes a radius calculation unit 12 that recognizes an approximate circle C for the arc-shaped portion A and calculates the radius R of the approximate circle C, a virtual liquid level height calculation unit 13 that calculates the virtual liquid level height of the liquid surface S, a correction value storage unit 14 that stores a correction value set based on the radius R of the approximate circle C and the liquid level height measured by experiment, and an actual liquid level height calculation unit 15 that corrects the virtual liquid level height H' calculated by the virtual liquid level height calculation unit 13 using the radius R of the approximate circle C calculated by the radius calculation unit 12 and the correction value of the correction value storage unit 14 to calculate the actual actual liquid level height H. Hereinafter, with reference to FIG. 5, the procedure for calculating the actual liquid level height H will be described together with each part constituting the image processing means 11.

[0014] When the photographing means 4 photographs the container 1, the radius calculation unit 12 recognizes an approximate circle C based on the arc-shaped portion A formed by the liquid surface S, and further calculates the radius R of the approximate circle C. Specifically, the radius calculation unit 12 performs binarization processing on the image photographed by the photographing means 4, and recognizes the arc-shaped portion A formed by the liquid surface S from the boundary line between the dark portion indicating the liquid and the bright portion indicating the space. Then, the radius calculation unit 12 calculates an approximate circle C approximating the recognized arc-shaped portion A and calculates the radius R of the approximate circle C. The method for recognizing the approximate circle C is conventionally known. For example, a method of selecting three or more pixels of the arc-shaped portion A and calculating a circle passing through these pixels can be used.

[0015] Subsequently, the virtual liquid level height calculation unit 13 calculates the height of the virtual liquid surface S in the container 1 from the image photographed by the photographing means 4 as the virtual liquid level height. Specifically, the virtual liquid level height calculation unit 13 first uses the approximate circle C obtained by the radius calculation unit 12 to recognize the intersection points B' between the approximate circle C and the wall surface of the container 1, and creates a reference line B connecting the intersection points B'. Specifically, from the image binarized by image processing, the boundary line between the dark part and the bright part is recognized as the wall surface of the container 1, and the point where the wall surface of the container 1 intersects the approximate circle C is recognized as the intersection point B' between the approximate circle C and the wall surface of the container 1. The reference line B is a line connecting the intersection points B'. However, if there is a height difference between one intersection point B' and the other intersection point B', the reference line B is created horizontally at a position that is the average of the heights of these intersection points B'. Next, the virtual liquid level height calculation unit 13 recognizes the vertex P of the approximate circle C obtained by the radius calculation unit 12, measures the distance from the vertex P of the approximate circle C to the reference line B, and calculates the height that is half of the distance as the virtual liquid level height H'. Here, required coordinate values are set for the imaging range imaged by the imaging means 4 in the image processing means 11, and the virtual liquid level height calculation unit 13 recognizes the virtual liquid level height H' based on these coordinate values. Note that as the position of the virtual liquid level height H', in addition to setting it at a position that is half of the distance between the vertex P of the approximate circle C and the reference line B described above, it may also be set at the position of the reference line B or the position of the vertex P of the approximate circle C.

[0016] A correction value N set based on a previously conducted experiment is registered in the correction value storage unit 14. In the filling line, when an abnormality occurs in the devices on the upstream side or the downstream side of the liquid level height inspection device 2, it is possible to change the conveyance speed of the container 1. In the liquid level height inspection device 2, the rotation speed of the rotating body 3 is changed to synchronize the conveyance speed of the container 1. When the rotation speed of the rotating body 3 is changed, as described above, the inclination angle of the liquid surface S fluctuates, and accordingly, the shape of the arc-shaped portion A also deforms. For example, when the rotation speed of the rotating body 3 is increased, a large centrifugal force acts on the container 1, so the inclination angle of the liquid surface S increases and the radius R of the approximate circle C decreases. The correction value N is the difference between the virtual liquid level height H' calculated by the virtual liquid level height calculation unit 13 and the actual liquid level height H. FIG. 6 is a graph with the radius R of the approximate circle C on the horizontal axis and the correction value N on the vertical axis. The correction value N is obtained by experiments conducted in advance. While transporting the actual container 1 filled with the actual liquid by the rotating body 3, it is photographed by the photographing means 4, and the radius R of the approximate circle C and the virtual liquid surface height H' are calculated by the radius calculation unit 12 and the virtual liquid surface height calculation unit 13. Then, the difference between the actual liquid surface height H contained in the container 1 and the virtual liquid surface height H' is calculated as the correction value N, and this is the result of collecting while varying the rotation speed of the rotating body 3. Here, FIGS. 6(a) and (b) are graphs showing the relationship between the radius R of the approximate circle C and the correction value N when the same liquid is filled in containers 1 with different volumes. As shown in these graphs, it can be understood that as the radius R of the approximate circle C decreases, that is, as the rotation speed of the rotating body 3 increases, the correction value N for correcting the virtual liquid surface height H' also increases.

[0017] And the actual liquid surface height calculation unit 15 corrects the virtual liquid surface height H' using the correction value N corresponding to the radius R of the approximate circle C, and calculates the actual liquid surface height H of the liquid surface S. Specifically, when the radius calculation unit 12 calculates the radius R of the approximate circle C, the actual liquid surface height calculation unit 15 retrieves the correction value N corresponding to the radius R from the correction value storage unit 14, and further corrects the virtual liquid surface height H' calculated by the virtual liquid surface height calculation unit 13 with the correction value N to calculate the actual liquid surface height H. In the case of this embodiment, the virtual liquid surface height H' calculated by the virtual liquid surface height calculation unit 13 is the middle of the distance between the reference plane and the vertex P of the approximate circle C, and since the actual liquid surface height H is located below the virtual liquid surface height H', the actual liquid surface height H is calculated by performing a correction of subtracting the correction value N from the calculated virtual liquid surface height H'. Subsequently, the actual liquid surface height calculation unit 15 compares the calculated actual liquid surface height H with the liquid surface height of the container 1 as a good product set in advance. If the actual liquid surface height H is within a predetermined range, the container 1 is determined to be a good product, and if it is outside the range, the container 1 is determined to be a defective product.

[0018] Thus, according to the liquid level height inspection device 2 of this embodiment, even when the liquid level S of the liquid is inclined due to the centrifugal force caused by the rotation of the rotating body 3, the actual liquid level height H can be accurately measured, and thereby the quality of the filling amount of the liquid into the container 1 can be accurately determined.

[0019] FIG. 7 illustrates a procedure for calculating the actual liquid level height H using the liquid level height inspection device 2 according to the second embodiment. Similar to the liquid level height inspection device 2 of the first embodiment, the liquid level height inspection device 2 according to the second embodiment also transports the container 1 by the rotating body 3, and the container 1 is photographed by the photographing means 4 provided inside the transport path of the container 1, so as to recognize the arc-shaped portion A of the inclined liquid level S. Further, the liquid level height inspection device 2 of this embodiment includes a transport speed measurement means for measuring the transport speed of the container 1 by the rotating body 3. As the transport speed measurement means, for example, a method of directly measuring by a phototube can be used, but in this embodiment, the rotation speed of the rotating body 3 measured by an encoder provided on the rotating body 3 is directly adopted as the transport speed. The image processing means 11 of the second embodiment includes a virtual liquid level height calculation unit that calculates the virtual liquid level height H' of the liquid level S, a correction value storage unit that stores a correction value N set based on the transport speed of the container 1 and a previously measured liquid level height, and the transport speed of the container 1 measured by the transport speed measurement means and the correction value N of the correction value storage unit are used to correct the virtual liquid level height H' calculated by the virtual liquid level height calculation unit, and an actual liquid level height calculation unit that calculates the actual actual liquid level height H.

[0020] The virtual liquid level height calculation unit performs the same processing as the virtual liquid level height calculation unit 13 in the first embodiment to recognize the intersection point B' between the approximate circle C and the wall surface of the container 1, and create a reference line B connecting the intersection points B'. Next, the virtual liquid level height calculation unit 13 measures the distance from the vertex P of the approximate circle C obtained by the vertex calculation unit to the reference line B, and calculates the position of half of the distance as the virtual liquid level height H'.

[0021] The correction value storage unit stores the correction value N measured by experiments conducted in advance, similar to the correction value storage unit 14 in the first embodiment. In this embodiment, the correction value N is calculated as follows: while the actual container 1 filled with the actual liquid is being conveyed by the rotating body 3, it is photographed by the photographing means 4, and the temporary liquid surface height H' is calculated by the temporary liquid surface height calculation unit. The difference between the temporary liquid surface height H' at that time and the actual liquid surface height is calculated as the correction value N. For example, this is collected while increasing the rotational speed of the rotating body 3 in increments of 10 rpm from 100 rpm, so that the correction value N for each conveying speed (rotational speed) can be obtained. In the case of this embodiment, as the conveying speed of the container 1 increases, the correction value N for correcting the temporary liquid surface height H' increases.

[0022] Then, the actual liquid surface height calculation unit corrects the temporary liquid surface height H' using the correction value N corresponding to the conveying speed of the container 1 measured by the conveying speed measurement means, and calculates the actual liquid surface height H of the liquid in the container 1. Specifically, when the actual liquid surface height calculation unit 15 calculates the conveying speed of the container 1 measured by the conveying speed measurement means, it extracts the correction value N corresponding to the conveying speed from the correction value storage unit 14, and corrects the temporary liquid surface height H' calculated by the temporary liquid surface height calculation unit 13 by the correction value N to calculate the actual actual liquid surface height H. In the case of this embodiment, the temporary liquid surface height H' calculated by the temporary liquid surface height calculation unit 13 is the middle of the distance between the reference plane and the vertex P of the approximate circle C, and since the actual liquid surface height H is located below the temporary liquid surface height H', the actual liquid surface height H is calculated by performing a correction of subtracting the correction value N from the calculated temporary liquid surface height H'. Subsequently, the actual liquid surface height calculation unit 15 compares the calculated actual liquid surface height H with the liquid surface height of the container 1 as a good product set in advance. If the actual liquid surface height H is within a predetermined range, the container 1 is determined to be a good product, and if it is outside the range, the container 1 is determined to be a defective product.

[0023] Thus, even when the liquid surface S in the container 1 is inclined due to the centrifugal force caused by the rotation of the rotating body 3, the liquid level height inspection apparatus 2 of the second embodiment can accurately measure the actual liquid level height H, and thereby accurately determine whether the filling amount of the liquid into the container 1 is good or not.

Explanation of Signs

[0024] 1 Container 2 Liquid level height inspection apparatus 3 Rotating body 4 Photographing means 11 Image processing means 12 Radius calculation unit 13 Temporary liquid level height calculation unit 14 Correction value storage unit 15 Actual liquid level height calculation unit A Arc-shaped part B Reference line C Approximate circle H Actual liquid level height H' Temporary liquid level height N Correction value S Liquid surface

Claims

1. A rotating body having a holding portion for holding a container filled with a liquid, imaging means for imaging the container conveyed by the rotating body, and image processing means for image-processing the image captured by the imaging means. In the liquid level height inspection device, the imaging means images the liquid level of the liquid inclined inside the container by the centrifugal force caused by the rotation of the rotating body, and the image processing means recognizes the liquid level height of the liquid in the container from the captured image. The imaging means is provided inside or outside the conveyance path of the container to image the arc-shaped portion formed by the edge of the inclined liquid level. The image processing means includes a radius calculation unit that recognizes an approximate circle of the arc-shaped portion and calculates the radius of the approximate circle, a temporary liquid level height calculation unit that calculates a temporary liquid level height from the arc-shaped portion, a correction value storage unit that stores a correction value set based on the radius R of the approximate circle and the liquid level height measured by experiment, and an actual liquid level height calculation unit that corrects the temporary liquid level height calculated by the temporary liquid level height calculation unit using the radius R of the approximate circle calculated by the radius calculation unit and the correction value of the correction value storage unit to calculate the actual liquid level height. The liquid level height inspection device is characterized by this.

2. The temporary liquid level height calculation unit recognizes the wall surface of the container from the captured image, and further calculates the temporary liquid level height using a reference line connecting the intersections of the approximate circle of the arc-shaped portion and the wall surface. The liquid level height inspection device according to Claim 1 is characterized by this.

Images